The present invention relates to the treatment of subterranean formations. More particularly, the present invention relates to compositions and methods utilizing swellable elastomers in subterranean operations.
In subterranean operations, there may be several instances where it may be desirable to control or prevent the passage of fluid through a portion of a subterranean formation, control or prevent the production of an undesirable fluid through a well bore, and/or isolate specific areas in a well bore or zones in a subterranean formation. However, in many instances, it may be problematic to do these things for a variety of reasons.
A variety of methods have been employed in an attempt to address the above mentioned problems. For example, improved cement compositions have been used in cementing operations in an effort to prevent, inter alia, the failure of the cement and/or the formation of voids, cracks, fractures, holes and/or channels that may form in the cement. In addition, several remedial cementing methods have been developed. For example, one type of remedial cementing is commonly referred to as “squeeze cementing,” and usually involves a method of preventing undesirable movement of oil, gas, or water through small holes or cracks in pipes disposed in the well bore; or annular spaces between the cement sheath and the pipe or walls of the well bore in permeable zones or fractures in subterranean formations by squeezing hydraulic sealant compositions, such as cement, therein which harden and form impermeable plugs.
Additionally, spacer fluids have been utilized to, inter alia, enhance drilling fluid and filter cake removal from the walls of a well bore. It is thought that inadequate removal of a filter cake from the walls of a well bore may result in a lack of a competent seal between the cement sheath and the well bore. Spacer fluids may be used to displace one fluid, such as a drilling fluid, in a well bore before entry into the well bore of another fluid, such as a cement composition. Among other things, a spacer fluid may be used not only to enhance drilling fluid and filter cake removal from the walls of well bores, but also to enhance solids removal during drilling operations, enhance displacement efficiency, and/or to physically separate chemically incompatible fluids. For example, in primary cementing, the cement composition may be separated from the drilling fluid and partially dehydrated drilling fluid may be removed from the walls of the well bore by placing a spacer fluid into the well bore between the drilling fluid and the cement composition.
Also, several methods have been utilized in an effort to prevent fluid loss and/or the undesirable production of water. For example, to prevent fluid loss and/or the undesirable production of water, additives commonly may be included in the treatment fluids. Examples of commonly used additives include, but are not limited to, gelling agents, such as hydroxyethylcellulose and xanthan. In addition, compounds referred to as relative permeability modifiers (“RPMs”) have been utilized to decrease the production of undesirable water. One example of a commonly used RPM includes polyacrylamide. These conventional methods commonly work at the well bore and/or formation face, however, in some instances formation damage may occur. Additionally, the use of crosslinked fluids may impact fracture geometry, for example, creating wider, shorter fractures.
Swellable elastomers have heretofore been utilized in some subterranean operations, for example, zonal isolation methods. Swellable elastomers usually include materials that swell upon contact with a particular fluid. In some methods, these swellable elastomers are used in conjunction with packers that are placed in the annulus of a well bore. The packer is contacted with a specific fluid so that the swellable elastomer present in the packer expands to seal the annular space. While this method of sealing an annular space has generally been effective, a need still exists for other methods directed to preventing the undesirable passage of fluids.